A major focus of the polyolefin industry in recent years has been on the development of new catalysts that deliver new and improved products. In this regard, metallocene catalysts, for example, are now widely used to produce polyolefin polymers, such as polyethylene polymers. While there are many advantages to using metallocene catalysts in olefin polymerization, there remain significant challenges. For example, metallocene catalysts, in particular supported metallocene catalysts, may be more prone to causing reactor fouling which may cause disruption and premature shutdown of the reactor. This is particularly the case in particle forming processes, such as gas and slurry phase processes. Adding other reagents to the polymerization process, such as antifouling agents or continuity additives/aids or continuity compositions, have been used to address such fouling issues.
In order to address reactor fouling problems caused by high activity metallocene catalysts, additives such as metal carboxylate salts may be added to the process, either separately or as part of the supported catalyst composition, such as in U.S. Pat. Nos. 6,608,153, 6,300,436 and 5,283,278.
U.S. Pat. Appln. Pubn. No. 2010/0292418 discloses a process for producing olefin based polymers in the presence of a continuity composition comprising an aluminum carboxylate and a fatty amine alkoxylate. The composition is prepared by mixing, for example, solid aluminum distearate and solid ethoxylated stearyl amine in mineral oil. The particular ethoxylated stearyl amine utilized is a commercially available form designated as AS-990, which contains ethoxylated stearyl amine and particulate silica.
However, components employed to address reactor fouling, such as the above mentioned metal carboxylate salts and/or fatty amines, often present handing difficulties. For example continuity compositions based on such components may be time consuming to prepare and often show inconsistent behavior. Mixing solid components, even under slurry conditions, can result in the formation of agglomerates which may adversely affect flowability and make the solid or slurry difficult to dry to the low moisture levels desirable for olefin polymerization. The use of higher temperature drying can be detrimental as this may cause the viscosity of a slurry derived from solid components to significantly increase, possibly through gelling mechanisms, making the slurry difficult to handle.
Therefore, despite the various continuity compositions known, challenges remain. Thus, it would be desirable to provide continuity compositions useful in olefin polymerization that are advantageous to prepare and handle and are also capable of operating in a polymerization process continuously with enhanced reactor operability.